Marantz 2325 receiver broke wire on mode switch?

[zedex]

I have a signal generator and scope.

 

[AE Bob]

The first thing I would do is inject a signal into the main amp inputs. I think you may need to plug an RCA connector into the preamp outputs to disconnect the pre/main switches in the jacks. You can just Y the signal generator so you can plug into both main inputs at once. Start at a low signal level, and increase the signal gradually until you have a moderate output. Run the unit a while, and see if the main amps are working properly. That will eliminate much of the circuitry. If the main amps produce crackling noises or something, then I would start there with troubleshooting and repair.

You can inject a signal into the left and right auxiliary inputs, and look at the signal going to the power amps, at the preamp output jacks, with a scope.

This should at least get you started figuring out what is wrong with your unit. This is TROUBLESHOOTING

I have seen a Marantz integrated amp with a Dolby board in it, where all (10 or 12) of the 10 uf 16 volt capacitors on the board were defective. They were all leaking DC to the next stage, causing all sorts of issues. The issue was only present if the Dolby was turned on though
The customer wanted it fixed because he wanted to turn Dolby on, have the Dolby meter (little vertically oriented meter in the middle of the amp face), active when he played it. I did replace them all, and looked elsewhere in the amp, but found none anywhere else.

 

[zedex]

Thanks AE Bob. Im going to replace all the caps on the dolby board anyways . And yes there are about a dozen of them and a 220 as well. I will give your troubleshooting guide a go.